The proximal ligamentous component of the triangular fibrocartilage complex

The proximal ligamentous component of the triangular fibrocartilage complex (TFCC) was studied anatomically using 15 fresh-frozen cadaver hand forearm specimens. Changes in the length of either side of this component were analysed during forearm rotation with the complete three-dimensional structure of the TFCC preserved. The proximal ligamentous component consists of three portions: dorsal, central and palmar. The dorsal and palmar portions connect the radius and ulna directly. These were recognized in all specimens whereas the central portion was not constant. The morphology of the proximal component was categorized into three types: fan-shaped, V-shaped, and funnel-shaped in five wrists each. Changes in ligament length during forearm rotation were measured using fine wires under slight tension that paralleled the ligaments from origin to insertion. The dorsal and palmar portions demonstrated three trends: the dorsal portion increased in length from supination to pronation whereas the palmar portion increased in length from pronation to supination; the length of the dorsal portion remained almost constant as the palmar portion increased in length from pronation to supination; the length of the palmar portion remained almost constant while the dorsal portion lengthened from supination to pronation. These variations appear to be related to which portion of the ligament was attached nearest to the centre of the ulnar fovea, where the rotational axis of the forearm passes. The portion attaching nearest to the fovea demonstrated a nearly isometric length pattern, whereas the portion which attached at a distance showed greater extensibility. These findings suggest that the proximal component of the TFCC corresponds to a true radioulnar ligament, and the isometric and eccentric fibres act mutually during forearm rotation.